Thursday, January 12, 2012

Largest dark matter map holds clues to dark energy: Heymans's team used the Canada-France-Hawaii Telescope to observe 10 million galaxies, each about 6 billion light years away. The researchers analysed the images to build a map of dark matter spanning 10 billion light years, the first direct glimpse of dark matter on such a large scale.
The map shows a great cosmic web, with scattered clumps of dark matter linked by wispy filaments...
The map also reaffirms the need for dark energy to account for the accelerating expansion of the universe. Some proposed alternatives say that, instead of invoking a whole new entity, physicists might simply need to tweak Einstein's theory of general relativity on very large scales. But the new map, which spans very large scales yet is consistent with general relativity, lets the air out of those theories. "So far," says Miller, "there is no observational evidence for any departure from Einstein's theory."